SINGAPORE, for the first time, has emerged as the most attractive investment destination in Asia for American companies, outperforming even China.

"The 10-year cumulative US investment in Singapore stood at US$138 billion (S$176.6 billion) at the end of 2012," United States Ambassador David Adelman, who leaves his post this week, told The Straits Times in an interview.

"You have now exceeded US investment into Japan and Australia, and you draw twice our investment into China. It is a credit to the Government of Singapore that it has created this very hospitable business climate in probably the best location in the world."

The 10-year investment figure - which jumped from US$116 billion the year before - is among the most visible highlights of the tightening strategic embrace between the most powerful nation and tiny Singapore, perhaps Asia's most admired country.

Mr Adelman, 49, highlighted two agreements that underscore the tight relationship - last year's strategic partnership dialogue agreement inked by Foreign Minister K. Shanmugam and then Secretary of State Hillary Clinton, and the US-Singapore Third Country Training Programme.

The first is reserved for only America's best friends while the proof of the latter's success is that in just 18 months, the two countries conducted no less than eight programmes for participants from Asean countries. Both programmes will pay long-term dividends, he predicted.

Meanwhile, according to US figures, Singapore investments in the US amounted to US$22 billion at the end of 2011.

People-level contacts also have accelerated, with 27,000 American residents on this island, thousands of Singaporean students enrolled in American universities and at any given time, between 800 and 1,000 Singapore military personnel training in the US.

Saying bilateral ties have "never been better", Mr Adelman said two broad elements had provided the potent mix that underscores the relationship.

First, the US rebalance towards Asia with Singapore as its anchor in South-east Asia. Second, this occurred at a time when Singapore was "an exceptionally willing partner".

While two-way trade - currently topping US$50 billion a year, overwhelmingly favouring the US - will increase and the strategic ties are set to deepen, one area that needs more attention is law enforcement cooperation.

"We have a strong, robust law enforcement relationship and we will continue to look for ways to strengthen it," he said, without elaborating.

The grandson of immigrants from Europe and the Middle East, Mr Adelman sounded a warning on the debate around foreigners in Singapore.

While Singapore had exceptional intellectual property protection and the rule of law, an important element of its attractiveness to foreign capital that must be preserved is its ability to draw talent from across the world, a factor that has even helped strengthen Singapore businesses.

"Government officials in Singapore recognise that. It is for them to strike a balance. American businesses and investors are watching it closely. I would even broaden it - all foreign investors are watching it very closely," he said.

Asked what he made of American scientist Shane Todd's death last year, since declared a suicide, Mr Adelman said dealing with tragedies was an unfortunate part of every ambassador's job.

He twice met the Todd family, who were inconsolable.

"Representatives of the US Embassy were present every minute during the coroner's proceedings, and we issued a statement at the conclusion that we believe was comprehensive, transparent and fair, and it adhered to the traditional standards of due process. We respect the decision."